Abstract: Abstract: Objective To investigate the high-risk factors leading to a poor prognosis of small renal cell carcinoma, and provide theoretical basis for the individualized treatment regimen. Methods This retrospective study analyzed the clini⁃ cal and histological data of 18 patients with small renal cell carcinoma treated in the Department of Urology of the Second Hospital of Tianjin Medical University from January 2004 to July 2015. All the patients underwent ultrasound, plain and en⁃ hanced CT examinations, also, received the surgeries. The tumor diameters, pathological types, pathological stages, Fuhrman grading of tumors and the prognosis of patients were analyzed. Results Preoperative CT examination revealed that 18 pa⁃ tients with the average tumor diameter of (3.1 ± 0.6) cm (ranged 2.0 to 4.0 cm). Five patients were diagnosed as T1aN0M0, 4 patients with T1aN0M1 (3 cases with lung metastasis, 1 case with brain metastasis), 3 patients with T1aN1M0 (CT examina⁃ tion showed a lymph node metastasis), 6 patients with T3aN0M0 (renal vein invasion or renal vein tumor thrombus). Patholog⁃ ical examination after surgery showed that 12 patients were Fuhrman grade Ⅱ, 5 were grade Ⅲ and 1 was grade Ⅳ;15 cases were clear cell carcinomas, 1 case was papillary carcinoma, 1 was hybrid cellular tumor (malignant rhabdoid tumor with sar⁃ comatoid differentiation) and the last case was sarcomatoid carcinoma renal cell carcinoma (Fuhrman grade V). 4 patients (T3a, Fuhrman grade Ⅱ) underwent retroperitoneal laparoscopic partial nephrectomy and the remaining underwent laparo⁃ scopic radical nephrectomy. The median follow-up time was 22.5 months (ranged 6 to 48 months). Four cases died (2 cases with tumor diameters of 3.8 cm and 4.0 cm at preliminary diagnosis， 2 cases with sarcomatoid renal carcinoma and 1 with brain metastasis), 1 case was lost. Other patients were found no tumor recurrence and metastasis. Conclusion The small re⁃ nal cell tumor with diameter≥3.0 cm, Fuhrman Ⅲ/Ⅳ grade， sarcomatoid cancer or metastasis should be considered as highrisk factors of small renal cell carcinoma. The high-risk small renal cell carcinoma is heterogeneous in its biological behav⁃ ior, which is expressed as aggressive growth and early invasion of renal tissue and even metastasis. The individualized treatment should be made based on preoperative imaging findings and postoperative pathology.

Key words: kidney neoplasms, diagnosis, neoplasm metastasis, risk factors, high-risk small renal carcinoma